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• Find location using only distance and bearing?

  - by pinnacler

  Triangulation works by checking your angle to three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and it's to my right at 90 degrees." Repeat 2 more times for different targets and angles. Trilateration works by checking your distance from three KNOWN targets. "I know the that's the Lighthouse of Alexandria, it's located here (X,Y) on a map, and I'm 100 meters away from that." Repeat 2 more times for different targets and ranges. But both of those methods rely on knowing WHAT you're looking at. Say you're in a forest and you can't differentiate between trees, but you know where key trees are. These trees have been hand picked as "landmarks." You have a robot moving through that forest slowly. Do you know of any ways to determine location based solely off of angle and range, exploiting geometry between landmarks? Note, you will see other trees as well, so you won't know which trees are key trees. Ignore the fact that a target may be occluded. Our pre-algorithm takes care of that. 1) If this exists, what's it called? I can't find anything. 2) What do you think the odds are of having two identical location 'hits?' I imagine it's fairly rare. 3) If there are two identical location 'hits,' how can I determine my exact location after I move the robot next. (I assume the chances of having 2 occurrences of EXACT angles in a row, after I reposition the robot, would be statistically impossible, barring a forest growing in rows like corn). Would I just calculate the position again and hope for the best? Or would I somehow incorporate my previous position estimate into my next guess? If this exists, I'd like to read about it, and if not, develop it as a side project. I just don't have time to reinvent the wheel right now, nor have the time to implement this from scratch. So if it doesn't exist, I'll have to figure out another way to localize the robot since that's not the aim of this research, if it does, lets hope it's semi-easy.

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• Delphi LoadLibrary Failing to find DLL other directory - any good options?

  - by Chris Thornton

  Two Delphi programs need to load foo.dll, which contains some code that injects a client-auth certificate into a SOAP request. foo.dll resides in c:\fooapp\foo.dll and is normally loaded by c:\fooapp\foo.exe. That works fine. The other program needs the same functionality, but it resides in c:\program files\unwantedstepchild\sadapp.exe. Both aps load the DLL with this code: FOOLib := LoadLibrary('foo.dll'); ... If FOOLib <> 0 then begin FOOProc := GetProcAddress(FOOLib , 'xInjectCert'); FOOProc(myHttpRequest, Data, CertName); end; It works great for foo.exe, as the dll is right there. sadapp.exe fails to load the library, so FOOLib is 0, and the rest never gets called. The sadapp.exe program therefore silently fails to inject the cert, and when we test against production, it the cert is missing, do the connection fails. Obviously, we should have fully-qualified the path to the DLL. Without going into a lot of details, there were aspects of the testing that masked this problem until recently, and now it's basically too late to fix in code, as that would require a full regression test, and there isn't time for that. Since we've painted ourselves into a corner, I need to know if there are any options that I've overlooked. While we can't change the code (for this release), we CAN tweak the installer. I've found that placing c:\fooapp into the path works. As does adding a second copy of foo.dll directly into c:\program files\unwantedstepchild. c:\fooapp\foo.exe will always be running while sadapp.exe is running, so I was hoping that Windows would find it that way, but apparently not. Is there a way to tell Windows that I really want that same DLL? Maybe a manifest or something? This is the sort of "magic bullet" that I'm looking for. I know I can: Modify the windows path, probably in the installer. That's ugly. Add a second copy of the DLL, directly into the unwantedstepchild folder. Also ugly Delay the project while we code and test a proper fix. Unacceptable. Other? Thanks for any guidance, especially with "Other". I understand that this issue is not necessarily specific to Delphi. Thanks!

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• Cocoa XML reader app

  - by Miskia

  Hello, I'm a newbie to Cocoa, just develop some little apps with C/C++ on Windows. I want to make a "simple" app on Cocoa. When the user specific XML file, the file nodes are represented "enduser viewable". I made an interface with some NSTextField. I made a subclass of NSDocument called "XMLFile" so i got "XMLFile.h" and "XMLFile.m" in my Xcode project. In the plist of my app i setup a new "Document Types": XML File - extensions: xml - role: view - class: XMLFile - store type: XML Here is my "XMLFile.h": #import <Cocoa/Cocoa.h> @interface FichierXML : NSDocument { } IBOutlet NSTextField *dateField; IBOutlet NSTextField *titleField; IBOutlet NSTextField *descField; IBOutlet NSTextField *vidfileField; IBOutlet NSTextField *imgfileField; IBOutlet NSObjectController *object; NSUInteger *mask; @end And here is my "XMLFile.m": #import "XMLFile.h" @implementation XMLFile - (BOOL)readFromData:(NSData *)datafile ofType:(NSString *)typeName error:(NSError **)outerror { NSMutableArray* ReportCreationDate = [[NSMutableArray alloc] initWithCapacity:10]; NSMutableArray* ReportTitle = [[NSMutableArray alloc] initWithCapacity:10]; NSMutableArray* ReportDescription = [[NSMutableArray alloc] initWithCapacity:10]; NSMutableArray* VideoPath = [[NSMutableArray alloc] initWithCapacity:10]; NSMutableArray* VideoThumbnailImageName = [[NSMutableArray alloc] initWithCapacity:10]; NSXMLDocument* doc = [[NSXMLDocument alloc] initWithData:datafile options:mask error:outerror]; NSXMLElement* root = [doc rootElement]; NSArray* dateElement = [root nodesForXPath:@"//Report/ReportCreationDate" error:nil]; for(NSXMLElement* xmlElement in dateElement) [dateElement setStringValue:[xmlElement stringValue]]; NSArray* titleElement = [root nodesForXPath:@"//Report/ReportTitle" error:nil]; for(NSXMLElement* xmlElement in titleElement) [titleField setStringValue:[xmlElement stringValue]]; NSArray* descElement = [root nodesForXPath:@"//Report/ReportDescription" error:nil]; for(NSXMLElement* xmlElement in descElement) [descField setStringValue:[xmlElement stringValue]]; NSArray* vidfileElement = [root nodesForXPath:@"//Report/Videos/Video/VideoPath" error:nil]; for(NSXMLElement* xmlElement in vidfileElement) [vidfileField setStringValue:[xmlElement stringValue]]; NSArray* imgfileElement = [root nodesForXPath:@"//Report/Videos/Video/VideoThumbnailImageName" error:nil]; for(NSXMLElement* xmlElement in imgfileElement) [imgfileField setStringValue:[xmlElement stringValue]]; [doc release]; [ReportCreationDate release]; [ReportTitle release]; [ReportDescription release]; [VideoPath release]; [VideoThumbnailImageName release]; return YES; } @end So. The user open the XMLFile, and XMLDocument analyse the file to extract nodes' data and send it to the differents NSTextField... But it doesn't work :( If someone can help me... I'm a newbie so don't be too rude if I made big mistakes :) Miskia.

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• How to best integrate generated code

  - by Arne

  I am evaluating the use of code generation for my flight simulation project. More specifically there is a requirement to allow "the average engineer" (no offense I am one myself) to define the differential equations that describe the dynamic system in a more natural syntax than C++ provides. The idea is to devise a abstract descriptor language that can be easily understood and edited to generate C++ code from. This descriptor is supplied by the modeling engineer and used by the ones implementing and maintaining the simulation evironment to generate code. I've got something like this in mind: model Aircraft has state x1, x2; state x3; input double : u; input bool : flag1, flag2; algebraic double : x1x2; model Engine : tw1, tw2; model Gear : gear; model ISA : isa; trim routine HorizontalFight; trim routine OnGround, General; constant double : c1, c2; constant int : ci1; begin differential equations x1' = x1 + 2.*x2; x2' = x2 + x1x2; begin algebraic equations x1x2 = x1*x2 + x1'; end model It is important to retain the flexibility of the C language thus the descriptor language is meant to only define certain parts of the definition and implementation of the model class. This way one enigneer provides the model in from of the descriptor language as examplified above and the maintenance enigneer will add all the code to read parameters from files, start/stop/pause the execution of the simulation and how a concrete object gets instatiated. My first though is to either generate two files from the descriptor file: one .h file containing declarations and one .cpp file containing the implementation of certain functions. These then need to be #included at appropriate places [File Aircarft.h] class Aircraft { public: void Aircraft(..); // hand-written constructor void ReadParameters(string &file_name); // hand-written private: /* more hand wirtten boiler-plate code */ /* generate declarations follow */ #include "Aircraft.generated.decl" }; [File Aircraft.cpp] Aircarft::Aircraft(..) { /* hand-written constructer implementation */ } /* more hand-written implementation code */ /* generated implementation code follows */ #include "Aircraft.generated.impl" Any thoughts or suggestions?

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• Visual Studio soft-crashing when encountering XAML Errors in initialize.

  - by Aren

  I've been having some serious issues with Visual Studio 2010 as of late. It's been crashing in a peculiar way when I encounter certain types of XAML errors during the InitializeComponent() of a control/window. The program breaks and visual studio gears up like it's catching an exception (because it is) and then stops midway displaying a broken highlight in my XAML file with no details as to what is wrong. Example: There is not pop outs, or details Anywhere about what is wrong, only a callstack that points to my InitializeComponent() call. Now normally I'd just do some trial and error to fix this problem, and find out where i messed up, but the real problem isn't my code. Visual Studio is rendered completely useless at this point. It reports my application still in "Running" mode. The Stop/Break/Restart buttons on the toolbar or in the menus don't do anything (but grey out). Closing the application does not stop this behaviour, closing visual studio gets it stuck in a massive loop where it yells at me complaining every file open is not in the debug project, then repeats this process when i have exausted every open file. I have to force-close devenv.exe, and after this happening 3-4 times in a row it's a lot of wasted time (as my projects are usually pretty big and studio can be quite slow @ loading). To the point Has anyone else experienced this? How can I stop studio from locking up. Can I at LEAST get information out of this beast another way so i can fix my XAML error sooner rather than after 3-4 trial-and-error compiles yielding the same crash? Any & All help would be appreciated. Visual Studio 2010 version: 10.0.30319.1RTM Edit & Update FWIW, mostly the errors that cause this are XamlParseExceptions (I figured this out after i found what was wrong with my XAML). I think I need to be clearer though, Im not looking for the solution to my code problem, as these are usually typos / small things, I'm looking for a solution to VStudio getting all buggered up as a result. The particular error in the above image that 100% for sure caused this was a XamlParseException caused by forgetting a Value attribute on a data trigger. I've fixed that part but it still doesn't tell my why my studio becomes a lump of neutered program when a perfectly normal exception is thrown in the parsing of the XAML. Code that will cause this issue (at least for me) This is the base template WPF Application, with the following Window.xaml code. The problem is a missing Value="True" on the <DataTrigger ...> in the template. It generates a XamlParseException and Visual Studio Crashes as described above when debugging it. Final Notes The following solutions did not help me: Restarting Visual Studio Rebooting Reinstalling Visual Studio

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• What happens when several Java servlet apps running on the same port ?

  - by Frank

  Something strange happened to my servlets and I think I've figured out why, yet I'm more confused. I used Netbean6.7 to develop a Paypal IPN (Instant Payment Notification) message servlet, it listens on port 8080 by default for Paypal IPN messages. I used some sample Java code from it's web site, but when it ran, only about 1 in 10 messages came through, and they looked correct, but why 1 in 10 ? Not 100% or none ? So I asked some questions here and got some advices, one in particular points me to Google's App Engine, so I downloaded it and ran the demo guestbook while my IPN servlet is still running on Netbeans, the strange thing happened, after I entered "appengine-java-sdk-1.3.2\bin\dev_appserver.cmd appengine-java-sdk-1.3.2\demos\guestbook\war" from the command prompt, I went to the following url on my browser "http://localhost:8080/", I thought I would see the Google demo guestbook page, NO, what I saw was another servlet I developed 2 years ago : "Web Academy", online course registration app. How can that happen ? I never started it, and I haven't touch that project for years. I guess because it's also listening on port 8080, so now I understand why the IPN messages only came through 1 in 10 times, because another servlet was also listening on that port and could have got the messages intended for IPN, or some how those two servlets' processes mixed up and therefore couldn't respond to Paypal properly, and failed. In order to verify some of my guesses, I turn off Netbeans, and ran the Google guestbook again at the prompt, this time on my browser http://localhost:8080/ points to the demo guestbook page. My Urls look like this : [A] Paypal IPN : http://localhost:8080/PayPal_App/PayPal_Servlet [B] Web Academy : http://localhost:8080/ So now, my questions are : <1> Why the "Web Academy" servlet was auto started when I ran the Paypal servlet ? <2> If I change the IPN listening port to 8083, would that mean I can run both of them on my PC at the same time without affecting each other ? <3> But I still don't understand, [A] and [B] look different, if a page for [A] is refreshed, it should show the Paypal content, and another page looking at [B] should show the Web Academy content, and that's exactly what happens when I started Netbeans to run the Paypal servlet, both pages show their respective content correctly side by side without interfering with each other, how come the IPN messages couldn't get through 100% of the time ? <4> In Netbeans how to assign 8080 to servlet [A] and assign port 8083 to servlet [B] ? <5> How to turn off auto start of Web Academy by Netbeans ?

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• Android Facebook SDK : post message without showing facebook page

  - by someone_ smiley

  I am trying to integrate Facebook to my Android app for social post. I have downloaded latest Facebook sdk from here and apply all setup require to post to facebook. Now i can post to facebook. But problem is that, when i run sample program from facebook sdk, a browser like page is open and user have to enter message himself there. but i dont want this page to showed up. i want a fixed message to post directly without opening facebook dialog box. But if there is noway to avoid this, please tell me how can i fixed certain part of message so that user can't modified it. Thanks in Advance Edit: this is message i got after using this project 04-10 11:44:34.691: I/dalvikvm(719): Failed resolving Lnet/xeomax/TestRocket/TestRocket; interface 22 'Lnet/xeomax/FBRocket/LoginListener;' 04-10 11:44:34.691: W/dalvikvm(719): Link of class 'Lnet/xeomax/TestRocket/TestRocket;' failed 04-10 11:44:34.691: D/AndroidRuntime(719): Shutting down VM 04-10 11:44:34.701: W/dalvikvm(719): threadid=1: thread exiting with uncaught exception (group=0x40015560) 04-10 11:44:34.781: E/AndroidRuntime(719): FATAL EXCEPTION: main 04-10 11:44:34.781: E/AndroidRuntime(719): java.lang.RuntimeException: Unable to instantiate activity ComponentInfo{net.xeomax.TestRocket/net.xeomax.TestRocket.TestRocket}: java.lang.ClassNotFoundException: net.xeomax.TestRocket.TestRocket in loader dalvik.system.PathClassLoader[/data/app/net.xeomax.TestRocket-1.apk] 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1569) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1663) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.access$1500(ActivityThread.java:117) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:931) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.os.Handler.dispatchMessage(Handler.java:99) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.os.Looper.loop(Looper.java:130) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.main(ActivityThread.java:3683) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.reflect.Method.invokeNative(Native Method) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.reflect.Method.invoke(Method.java:507) 04-10 11:44:34.781: E/AndroidRuntime(719): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839) 04-10 11:44:34.781: E/AndroidRuntime(719): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597) 04-10 11:44:34.781: E/AndroidRuntime(719): at dalvik.system.NativeStart.main(Native Method) 04-10 11:44:34.781: E/AndroidRuntime(719): Caused by: java.lang.ClassNotFoundException: net.xeomax.TestRocket.TestRocket in loader dalvik.system.PathClassLoader[/data/app/net.xeomax.TestRocket-1.apk] 04-10 11:44:34.781: E/AndroidRuntime(719): at dalvik.system.PathClassLoader.findClass(PathClassLoader.java:240) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.ClassLoader.loadClass(ClassLoader.java:551) 04-10 11:44:34.781: E/AndroidRuntime(719): at java.lang.ClassLoader.loadClass(ClassLoader.java:511) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.Instrumentation.newActivity(Instrumentation.java:1021) 04-10 11:44:34.781: E/AndroidRuntime(719): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1561) 04-10 11:44:34.781: E/AndroidRuntime(719): ... 11 more

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• Twisted: why is it that passing a deferred callback to a deferred thread makes the thread blocking a

  - by surtyaarthoughts

  I unsuccessfully tried using txredis (the non blocking twisted api for redis) for a persisting message queue I'm trying to set up with a scrapy project I am working on. I found that although the client was not blocking, it became much slower than it could have been because what should have been one event in the reactor loop was split up into thousands of steps. So instead, I tried making use of redis-py (the regular blocking twisted api) and wrapping the call in a deferred thread. It works great, however I want to perform an inner deferred when I make a call to redis as I would like to set up connection pooling in attempts to speed things up further. Below is my interpretation of some sample code taken from the twisted docs for a deferred thread to illustrate my use case: #!/usr/bin/env python from twisted.internet import reactor,threads from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(): print 'doing lookup... this may take a while' time.sleep(10) return 'results from redis' def result(res): print res def main(): lc = LoopingCall(main_loop) lc.start(2) d = threads.deferToThread(aBlockingRedisCall) d.addCallback(result) reactor.run() if __name__=='__main__': main() And here is my alteration for connection pooling that makes the code in the deferred thread blocking : #!/usr/bin/env python from twisted.internet import reactor,defer from twisted.internet.task import LoopingCall import time def main_loop(): print 'doing stuff in main loop.. do not block me!' def aBlockingRedisCall(x): if x<5: #all connections are busy, try later print '%s is less than 5, get a redis client later' % x x+=1 d = defer.Deferred() d.addCallback(aBlockingRedisCall) reactor.callLater(1.0,d.callback,x) return d else: print 'got a redis client; doing lookup.. this may take a while' time.sleep(10) # this is now blocking.. any ideas? d = defer.Deferred() d.addCallback(gotFinalResult) d.callback(x) return d def gotFinalResult(x): return 'final result is %s' % x def result(res): print res def aBlockingMethod(): print 'going to sleep...' time.sleep(10) print 'woke up' def main(): lc = LoopingCall(main_loop) lc.start(2) d = defer.Deferred() d.addCallback(aBlockingRedisCall) d.addCallback(result) reactor.callInThread(d.callback, 1) reactor.run() if __name__=='__main__': main() So my question is, does anyone know why my alteration causes the deferred thread to be blocking and/or can anyone suggest a better solution?

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• Component must be a valid peer (when i remove frame.add(Component);)

  - by boyd

  i have this code here for creating and drawing array of pixels into an image import javax.swing.JFrame; import java.awt.Canvas; import java.awt.Graphics; import java.awt.image.BufferStrategy; import java.awt.image.BufferedImage; import java.awt.image.DataBufferInt; public class test extends Canvas implements Runnable{ private static final long serialVersionUID = 1L; public static int WIDTH = 800; public static int HEIGHT = 600; public boolean running=true; public int[] pixels; public BufferedImage img; public static JFrame frame; private Thread thread; public static void main(String[] arg) { test wind = new test(); frame = new JFrame("WINDOW"); frame.add(wind); frame.setVisible(true); frame.setSize(WIDTH, HEIGHT); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); wind.init(); } public void init(){ thread=new Thread(this); thread.start(); img=new BufferedImage(WIDTH, HEIGHT,BufferedImage.TYPE_INT_RGB); pixels=((DataBufferInt)img.getRaster().getDataBuffer()).getData(); } public void run(){ while(running){ render(); try { thread.sleep(55); } catch (InterruptedException e) { e.printStackTrace(); } } } public void render(){ BufferStrategy bs=this.getBufferStrategy(); if(bs==null){ createBufferStrategy(4); return; } drawRect(0,0,150,150); Graphics g= bs.getDrawGraphics(); g.drawImage(img, 0, 0, WIDTH, HEIGHT, null); g.dispose(); bs.show(); } private void drawRect(int x, int y, int w, int h) { for(int i=x;i<w;i++) for(int j=x;j<h;j++) pixels[i+j*WIDTH]=346346; } } Why i get "Component must be a valid peer" error when i remove the line: frame.add(wind); Why I want to remove it? Because I want to create a frame using a class object(from another file) and use the code Window myWindow= new Window() to do exactly the same thing BTW: who knows Java and understands what i wrote please send me a message with your skype or yahoo messenger id.I want to cooperate with you for a project (graphics engine for games)

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• Calling/selecting variables (float valued) with user input in Python

  - by Jonathan Straus

  I've been working on a computational physics project (plotting related rates of chemical reactants with respect to eachother to show oscillatory behavior) with a fair amount of success. However, one of my simulations involves more than two active oscillating agents (five, in fact) which would obviously be unsuitable for any single visual plot... My scheme was hence to have the user select which two reactants they wanted plotted on the x-axis and y-axis respectively. I tried (foolishly) to convert string input values into the respective variable names, but I guess I need a radically different approach if any exist? If it helps clarify any, here is part of my code: def coupledBrusselator(A, B, t_trial,display_x,display_y): t = 0 t_step = .01 X = 0 Y = 0 E = 0 U = 0 V = 0 dX = (A) - (B+1)*(X) + (X**2)*(Y) dY = (B)*(X) - (X**2)*(Y) dE = -(E)*(U) - (X) dU = (U**2)*(V) -(E+1)*(U) - (B)*(X) dV = (E)*(U) - (U**2)*(V) array_t = [0] array_X = [0] array_Y = [0] array_U = [0] array_V = [0] while t <= t_trial: X_1 = X + (dX)*(t_step/2) Y_1 = Y + (dY)*(t_step/2) E_1 = E + (dE)*(t_step/2) U_1 = U + (dU)*(t_step/2) V_1 = V + (dV)*(t_step/2) dX_1 = (A) - (B+1)*(X_1) + (X_1**2)*(Y_1) dY_1 = (B)*(X_1) - (X_1**2)*(Y_1) dE_1 = -(E_1)*(U_1) - (X_1) dU_1 = (U_1**2)*(V_1) -(E_1+1)*(U_1) - (B)*(X_1) dV_1 = (E_1)*(U_1) - (U_1**2)*(V_1) X_2 = X + (dX_1)*(t_step/2) Y_2 = Y + (dY_1)*(t_step/2) E_2 = E + (dE_1)*(t_step/2) U_2 = U + (dU_1)*(t_step/2) V_2 = V + (dV_1)*(t_step/2) dX_2 = (A) - (B+1)*(X_2) + (X_2**2)*(Y_2) dY_2 = (B)*(X_2) - (X_2**2)*(Y_2) dE_2 = -(E_2)*(U_2) - (X_2) dU_2 = (U_2**2)*(V_2) -(E_2+1)*(U_2) - (B)*(X_2) dV_2 = (E_2)*(U_2) - (U_2**2)*(V_2) X_3 = X + (dX_2)*(t_step) Y_3 = Y + (dY_2)*(t_step) E_3 = E + (dE_2)*(t_step) U_3 = U + (dU_2)*(t_step) V_3 = V + (dV_2)*(t_step) dX_3 = (A) - (B+1)*(X_3) + (X_3**2)*(Y_3) dY_3 = (B)*(X_3) - (X_3**2)*(Y_3) dE_3 = -(E_3)*(U_3) - (X_3) dU_3 = (U_3**2)*(V_3) -(E_3+1)*(U_3) - (B)*(X_3) dV_3 = (E_3)*(U_3) - (U_3**2)*(V_3) X = X + ((dX + 2*dX_1 + 2*dX_2 + dX_3)/6) * t_step Y = Y + ((dX + 2*dY_1 + 2*dY_2 + dY_3)/6) * t_step E = E + ((dE + 2*dE_1 + 2*dE_2 + dE_3)/6) * t_step U = U + ((dU + 2*dU_1 + 2*dY_2 + dE_3)/6) * t_step V = V + ((dV + 2*dV_1 + 2*dV_2 + dE_3)/6) * t_step dX = (A) - (B+1)*(X) + (X**2)*(Y) dY = (B)*(X) - (X**2)*(Y) t_step = .01 / (1 + dX**2 + dY**2) ** .5 t = t + t_step array_X.append(X) array_Y.append(Y) array_E.append(E) array_U.append(U) array_V.append(V) array_t.append(t) where previously display_x = raw_input("Choose catalyst you wish to analyze in the phase/field diagrams (X, Y, E, U, or V) ") display_y = raw_input("Choose one other catalyst from list you wish to include in phase/field diagrams ") coupledBrusselator(A, B, t_trial, display_x, display_y) Thanks!

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• Qt vs .NET - a few comparisons [closed]

  - by Pirate for Profit

  Event Handling In Qt the event handling system you just emit signals when something cool happens and then catch them in slots, for instance emit valueChanged(int percent, bool something); and void MyCatcherObj::valueChanged(int p, bool ok){} blocking them and disconnecting them when needed, doing it across threads... once you get the hang of it, it just seems a lot more natural and intuitive than the way the .NET event handling is set up (you know, object sender, CustomEventArgs e). And I'm not just talking about syntax, because in the end the .NET delegate crap is the bomb. I'm also talking about in more than just reflection (because, yes, .NET obviously has much stronger reflection capabilities). I'm talking about in the way the system feels to a human being. Qt wins hands down i m o. Basically, the footprints make more sense and you can visualize the project easier without the clunky event handling system. I wish I could it explain it better. The only thing is, I do love some of the ease of C# compared to C++ and .NET's assembly architecture. That is a big bonus for modular projects, which are a PITA to do in C++. Database Ease of Doing Crap Also what about datasets and database manipulations. I think .net wins here but I'm not sure. Threading/Conccurency How do you guys think of the threading? In .NET, all I've ever done is make like a list of master worker threads with locks. I like QConcurrentFramework, you don't worry about locks or anything, and with the ease of the signal slot system across threads it's nice to get notified about the progress of things. Memory Usage Also what do you think of the overall memory usage comparison. Is the .NET garbage collector pretty on the ball and quick compared to the instantaneous nature of native memory management? Or does it just let programs leak up a storm and lag the computer then clean it up when it's about to really lag? However, I am a n00b who doesn't know what I'm talking about, please school me on the subject.

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• UIImageWriteToSavedPhotosAlbum showing memory leak with iPhone connected to Instruments

  - by user168739

  Hi, I'm using version 3.0.1 of the SDK. With the iPhone connected to Instruments I'm getting a memory leak when I call UIImageWriteToSavedPhotosAlbum. Below is my code: NSString *gnTmpStr = [NSString stringWithFormat:@"%d", count]; UIImage *ganTmpImage = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:gnTmpStr ofType:@"jpg"]]; // Request to save the image to camera roll UIImageWriteToSavedPhotosAlbum(ganTmpImage, self, @selector(imageSavedToPhotosAlbum:didFinishSavingWithError:contextInfo:), nil); and the selector method - (void)imageSavedToPhotosAlbum:(UIImage *)image didFinishSavingWithError:(NSError *)error contextInfo:(void *)contextInfo { NSString *message; NSString *title; if (!error) { title = @"Wallpaper"; message = @"Wallpaper Saved"; } else { title = @"Error"; message = [error description]; } UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:message delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [alert show]; [alert release]; } Am I forgetting to release something once the image has been saved and the selector method imageSavedToPhotosAlbum is called? Or is there a possible known issue with UIImageWriteToSavedPhotosAlbum? Here is the stack trace from Instruments: Leaked Object: GeneralBlock-3584 size: 3.50 KB 30 MyApp start 29 MyApp main /Users/user/Desktop/MyApp/main.m:14 28 UIKit UIApplicationMain 27 UIKit -[UIApplication _run] 26 GraphicsServices GSEventRunModal 25 CoreFoundation CFRunLoopRunInMode 24 CoreFoundation CFRunLoopRunSpecific 23 GraphicsServices PurpleEventCallback 22 UIKit _UIApplicationHandleEvent 21 UIKit -[UIApplication sendEvent:] 20 UIKit -[UIWindow sendEvent:] 19 UIKit -[UIWindow _sendTouchesForEvent:] 18 UIKit -[UIControl touchesEnded:withEvent:] 17 UIKit -[UIControl(Internal) _sendActionsForEvents:withEvent:] 16 UIKit -[UIControl sendAction:to:forEvent:] 15 UIKit -[UIApplication sendAction:toTarget:fromSender:forEvent:] 14 UIKit -[UIApplication sendAction:to:from:forEvent:] 13 CoreFoundation -[NSObject performSelector:withObject:withObject:] 12 UIKit -[UIBarButtonItem(Internal) _sendAction:withEvent:] 11 UIKit -[UIApplication sendAction:to:from:forEvent:] 10 CoreFoundation -[NSObject performSelector:withObject:withObject:] 9 MyApp -[FlipsideViewController svPhoto] /Users/user/Desktop/MyApp/Classes/FlipsideViewController.m:218 8 0x317fa528 7 0x317e3628 6 0x317e3730 5 0x317edda4 4 0x3180fc74 3 Foundation +[NSThread detachNewThreadSelector:toTarget:withObject:] 2 Foundation -[NSThread start] 1 libSystem.B.dylib pthread_create 0 libSystem.B.dylib malloc I did a test with a new project and only added this code below in the viewDidLoad: NSString *gnTmpStr = [NSString stringWithFormat:@"DefaultTest"]; UIImage *ganTmpImage = [UIImage imageWithContentsOfFile:[[NSBundle mainBundle] pathForResource:gnTmpStr ofType:@"png"]]; // Request to save the image to camera roll UIImageWriteToSavedPhotosAlbum(ganTmpImage, nil, nil, nil); The same leak shows up right after the app loads Thank you for the help. Bryan

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• Buy or Build for web deployment?

  - by Cannonade

  I have been evaluating the wide range of installation and web deployment solutions available for Windows applications. I will just clarify here (without too much detail, these tools have been covered in other questions) my understanding of the options: NSIS - Free tool that generates setup executables. Small binary. Specialized, sometimes obtuse, scripting language. Inno Setup - Free tools for setup executables. Various binary compression schemes. Pascal scripting engine. WIX - Free toolset to generate MSI binaries. XML definitions language. WIX ClickThrough - Additional tools for packaging, web download and auto update detection (now part of WIX core). InstallShield - Commercial development environment for installation packaging. Generates MSI binaries. C-like InstallScript language. Wise - Commercial development environment for installation packaging. Generates MSI binaries. ClickOnce - Visual Studio supported framework for publishing applications to a webserver, with automatic detection of updates. No support for custom installation requirements (INI files, registry etc ...). Packages setup as an MSI binary. Install Aware - Commercial development environment for installation. Generates MSI binaries. Automatic Update framwork (Web Update). If I have missed any, please let me know. And found some useful discussions of these technologies on StackOverflow: Best Simple Install System Best choice for Windows installers Alternatives to ClickOnce I have worked with a few of these solutions, as well as a handful of proprietary internal installation solutions. They are mostly concerned with packing installations and providing a framework for developers to access the run time environment. With the growing requirement for web deployment and automatic software updates, I expected to find more of a consensus among developers on a framework for web delivery of software and subsequent updates, I haven't really found that consensus. There are certainly solutions available (ClickOnce, ClickThrough, InstallShield Update Service), but they each have considerable limitations (please correct me if I mis-represent any of these). I would be interested in a framework that provided some of the following: Third party hosting/management of updates. Access to client environment (INI files, registry, etc..). User registration/activation. Feedback/Error reporting This is leaving me with the strong impression that the best way to approach the web deployment problem is through a custom built proprietary solution (possibly leveraging existing installer packaging). I have seen this sort of solution work well for a number of successful applications: FileZilla - HTTP request to update.filezilla-project.org to check for updates, downloads an NSIS binary (I think) and then shuts down to run the install.

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• Combinations and Permutations in F#

  - by Noldorin

  I've recently written the following combinations and permutations functions for an F# project, but I'm quite aware they're far from optimised. /// Rotates a list by one place forward. let rotate lst = List.tail lst @ [List.head lst] /// Gets all rotations of a list. let getRotations lst = let rec getAll lst i = if i = 0 then [] else lst :: (getAll (rotate lst) (i - 1)) getAll lst (List.length lst) /// Gets all permutations (without repetition) of specified length from a list. let rec getPerms n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, _ -> lst |> getRotations |> Seq.collect (fun r -> Seq.map ((@) [List.head r]) (getPerms (k - 1) (List.tail r))) /// Gets all permutations (with repetition) of specified length from a list. let rec getPermsWithRep n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, _ -> lst |> Seq.collect (fun x -> Seq.map ((@) [x]) (getPermsWithRep (k - 1) lst)) // equivalent: | k, _ -> lst |> getRotations |> Seq.collect (fun r -> List.map ((@) [List.head r]) (getPermsWithRep (k - 1) r)) /// Gets all combinations (without repetition) of specified length from a list. let rec getCombs n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, (x :: xs) -> Seq.append (Seq.map ((@) [x]) (getCombs (k - 1) xs)) (getCombs k xs) /// Gets all combinations (with repetition) of specified length from a list. let rec getCombsWithRep n lst = match n, lst with | 0, _ -> seq [[]] | _, [] -> seq [] | k, (x :: xs) -> Seq.append (Seq.map ((@) [x]) (getCombsWithRep (k - 1) lst)) (getCombsWithRep k xs) Does anyone have any suggestions for how these functions (algorithms) can be sped up? I'm particularly interested in how the permutation (with and without repetition) ones can be improved. The business involving rotations of lists doesn't look too efficient to me in retrospect. Update Here's my new implementation for the getPerms function, inspired by Tomas's answer. Unfortunately, it's not really any fast than the existing one. Suggestions? let getPerms n lst = let rec getPermsImpl acc n lst = seq { match n, lst with | k, x :: xs -> if k > 0 then for r in getRotations lst do yield! getPermsImpl (List.head r :: acc) (k - 1) (List.tail r) if k >= 0 then yield! getPermsImpl acc k [] | 0, [] -> yield acc | _, [] -> () } getPermsImpl List.empty n lst

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• Accessing different connection strings at runtime in ASP.NET MVC 1

  - by Neil T.

  I'm trying to implement integration testing in my ASP.NET MVC 1.0 solution. The technologies in use are LINQ-to-SQL, NUnit and WatiN. I recently discovered a pattern that will allow me to create a testing version of the database on the fly without modifying the development version of the database. I needed this behavior in order to run my user interface tests in WatiN that may modify the database. The plan is to modify the connection string in the Web.config file, and pass that new connection string to the DataContext constructor. This way, I don't have to add routes or modify my URLs in order to perform the integration testing. I've set up the project so that the test setup can modify the connection string to point to the test database when the tests are running. The connection string is stored in web.config. The problem I'm having is that when I try to run the tests, I get a NullReferenceException when trying to access the HTTPContext. From everything that I have read so far, the HTTPContext is only available within the context of a controller. Here is the code for the property that is supposed to give me the reference to the Web.config file: private System.Configuration.Configuration WebConfig { get { ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap(); // NullReferenceException occurs on this line. fileMap.ExeConfigFilename = HttpContext.Current.Server.MapPath("~\\web.config"); System.Configuration.Configuration config = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None); return config; } } Is there something that I am missing in order to make this work? Is there a better way to accomplish what I'm trying to achieve? UPDATE: I decided to abandon the modification of Web.config in lieu of a "request-scoped DataContext" pattern that I found here. From the looks of it, I believe it should give me the results I'm looking for. However, during the TextFixtureSetUp, I try to create a new copy of the database for testing purposes, and it fails silently. When I get to the tests, the repository still uses the production database connection string to load data.

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• Checking a set of listbox items against a text box vb.net

  - by Shane Fagan

  Hi all I have this code to check if an item from a textbox is in a listbox and its giving me the error at the bottom. Any ideas what im doing wrong? I copied it from another part of my project and it was working for that part so I cant see whats wrong. If LocationsSearchTextBox.Text <> "" And LocationListBox.Items.Count > 0 Then tempInt = 0 While (tempInt < ClientListBox.Items.Count) If LocationListBox.Items(tempInt).ToString.Contains(LocationsSearchTextBox.Text) = False Then LocationListBox.Items.RemoveAt(tempInt) End If tempInt += 1 End While End If System.ArgumentOutOfRangeException was unhandled Message="InvalidArgument=Value of '2' is not valid for 'index'. Parameter name: index" ParamName="index" Source="System.Windows.Forms" StackTrace: at System.Windows.Forms.ListBox.ObjectCollection.get_Item(Int32 index) at AuctioneerProject.Viewing.LocationsSearchTextBox_KeyPress(Object sender, KeyPressEventArgs e) in C:\Users\admin\Desktop\Auctioneers\AuctioneerProject\AuctioneerProject\Viewing.vb:line 301 at System.Windows.Forms.Control.OnKeyPress(KeyPressEventArgs e) at System.Windows.Forms.Control.ProcessKeyEventArgs(Message& m) at System.Windows.Forms.Control.ProcessKeyMessage(Message& m) at System.Windows.Forms.Control.WmKeyChar(Message& m) at System.Windows.Forms.Control.WndProc(Message& m) at System.Windows.Forms.TextBoxBase.WndProc(Message& m) at System.Windows.Forms.TextBox.WndProc(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m) at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m) at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam) at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg) at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData) at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context) at System.Windows.Forms.Application.Run(ApplicationContext context) at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel() at Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine) at AuctioneerProject.My.MyApplication.Main(String[] Args) in 17d14f5c-a337-4978-8281-53493378c1071.vb:line 81 at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args) at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args) at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() at System.Threading.ThreadHelper.ThreadStart_Context(Object state) at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) at System.Threading.ThreadHelper.ThreadStart() InnerException:

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• JBOSS 7 encoding not working as expected

  - by Fofole

  I had problems with my listgrids not showing diacritcs corectly and I found out that when I inserted from java into the db the values where already bugged. A post here helped and I changed my project properties - Text encoding - other - UTF-8 and this fixed my problem. Thing is this only fixes my problem locally. What I need to do is on my Jboss server also set the encoding somehow. This is what I put in my configuration file: <?xml version='1.0' encoding='UTF-8'?> <server name="vali-ubuntu" xmlns="urn:jboss:domain:1.0"> extensions> extension module="org.jboss.as.clustering.infinispan"/> extension module="org.jboss.as.connector"/> extension module="org.jboss.as.deployment-scanner"/> extension module="org.jboss.as.ee"/> extension module="org.jboss.as.ejb3"/> extension module="org.jboss.as.jaxrs"/> extension module="org.jboss.as.jmx"/> extension module="org.jboss.as.logging"/> extension module="org.jboss.as.naming"/> extension module="org.jboss.as.osgi"/> extension module="org.jboss.as.remoting"/> extension module="org.jboss.as.sar"/> extension module="org.jboss.as.security"/> extension module="org.jboss.as.threads"/> extension module="org.jboss.as.transactions"/> extension module="org.jboss.as.web"/> extension module="org.jboss.as.weld"/> /extensions> system-properties> property name="org.apache.catalina.connector.URI_ENCODING" value="UTF-8"/> property name="org.apache.catalina.connector.USE_BODY_ENCODING_FOR_QUERY_STRING" value="tru e"/> /system-properties> //..... This doesn't work so maybe I need to add something else. I tried everything I could find with no succes so any help is appreciated. Thanks. EDIT:From what I read, this will work only in jboss 7.1.0 beta 1 or highier. (URIEncoding) and I use JBoss 7.0.2 so I need a replacement for 7.0.2

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• Stumbleupon type query...

  - by Chris Denman

  Wow, makes your head spin! I am about to start a project, and although my mySql is OK, I can't get my head around what required for this: I have a table of web addresses. id,url 1,http://www.url1.com 2,http://www.url2.com 3,http://www.url3.com 4,http://www.url4.com I have a table of users. id,name 1,fred bloggs 2,john bloggs 3,amy bloggs I have a table of categories. id,name 1,science 2,tech 3,adult 4,stackoverflow I have a table of categories the user likes as numerical ref relating to the category unique ref. For example: user,category 1,4 1,6 1,7 1,10 2,3 2,4 3,5 . . . I have a table of scores relating to each website address. When a user visits one of these sites and says they like it, it's stored like so: url_ref,category 4,2 4,3 4,6 4,2 4,3 5,2 5,3 . . . So based on the above data, URL 4 would score (in it's own right) as follows: 2=2 3=2 6=1 What I was hoping to do was pick out a random URL from over 2,000,000 records based on the current users interests. So if the logged in user likes categories 1,2,3 then I would like to ORDER BY a score generated based on their interest. If the logged in user likes categories 2 3 and 6 then the total score would be 5. However, if the current logged in user only like categories 2 and 6, the URL score would be 3. So the order by would be in context of the logged in users interests. Think of stumbleupon. I was thinking of using a set of VIEWS to help with sub queries. I'm guessing that all 2,000,000 records will need to be looked at and based on the id of the url it will look to see what scores it has based on each selected category of the current user. So we need to know the user ID and this gets passed into the query as a constant from the start. Ain't got a clue! Chris Denman

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• Not able to show video with html5

  - by shin

  I am testing html 5 video tag. I am using http://www.kaltura.org/project/HTML5_Video_Media_JavaScript_Library and http://camendesign.co.uk/. I downloaded the creative common video. When I use an external link, it plays the video. So I uploaded the video to my server but it does not play. It asks if I want to save it or asking an application to play. When I go to the external link, http://cdn.kaltura.org/apis/html5lib/kplayer-examples/media/bbb400p.ogv, it plays it on the browser automatically. I also tested locally, but it does not play either. I am hoping someone gives me why and how to solve the problem. This code works. <figure> <video id="vid1" width="500" height="300" style="position:absolute" poster="http://cdn.kaltura.org/apis/html5lib/kplayer-examples/media/bbb480.jpg" durationHint="33" controls = "true"> <source src="http://cdn.kaltura.org/apis/html5lib/kplayer-examples/media/bbb400p.ogv" /> <source src="http://cdn.kaltura.org/apis/html5lib/kplayer-examples/media/bbb_trailer_iphone.m4v"/> </video> </figure> This does not. <figure> <video id="vid1" width="500" height="300" style="position:absolute" poster="http://cdn.kaltura.org/apis/html5lib/kplayer-examples/media/bbb480.jpg" durationHint="33" controls = "true"> <source src="http://www.mywebsite.com/media/bbb400p.ogv" /> <source src="http://www.mywebsite.com/media/bbb_trailer_iphone.m4v"/> </video> </figure> This does not work either. <figure> <video id="vid1" width="500" height="300" style="position:absolute" poster="http://cdn.kaltura.org/apis/html5lib/kplayer-examples/media/bbb480.jpg" durationHint="33" controls = "true"> <source src="http://127.0.0.1/html5videotest/media/bbb400p.ogv" /> <source src="http://127.0.0.1/html5videotest/media/bbb_trailer_iphone.m4v"/> </video> </figure>

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• .Net Dynamically Load DLL

  - by hermiod

  I am trying to write some code that will allow me to dynamically load DLLs into my application, depending on an application setting. The idea is that the database to be accessed is set in the application settings and then this loads the appropriate DLL and assigns it to an instance of an interface for my application to access. This is my code at the moment: Dim SQLDataSource As ICRDataLayer Dim ass As Assembly = Assembly. _ LoadFrom("M:\MyProgs\WebService\DynamicAssemblyLoading\SQLServer\bin\Debug\SQLServer.dll") Dim obj As Object = ass.CreateInstance(GetType(ICRDataLayer).ToString, True) SQLDataSource = DirectCast(obj, ICRDataLayer) MsgBox(SQLDataSource.ModuleName & vbNewLine & SQLDataSource.ModuleDescription) I have my interface (ICRDataLayer) and the SQLServer.dll contains an implementation of this interface. I just want to load the assembly and assign it to the SQLDataSource object. The above code just doesn't work. There are no exceptions thrown, even the Msgbox doesn't appear. I would've expected at least the messagebox appearing with nothing in it, but even this doesn't happen! Is there a way to determine if the loaded assembly implements a specific interface. I tried the below but this also doesn't seem to do anything! For Each loadedType As Type In ass.GetTypes If GetType(ICRDataLayer).IsAssignableFrom(loadedType) Then Dim obj1 As Object = ass.CreateInstance(GetType(ICRDataLayer).ToString, True) SQLDataSource = DirectCast(obj1, ICRDataLayer) End If Next EDIT: New code from Vlad's examples: Module CRDataLayerFactory Sub New() End Sub ' class name is a contract, ' should be the same for all plugins Private Function Create() As ICRDataLayer Return New SQLServer() End Function End Module Above is Module in each DLL, converted from Vlad's C# example. Below is my code to bring in the DLL: Dim SQLDataSource As ICRDataLayer Dim ass As Assembly = Assembly. _ LoadFrom("M:\MyProgs\WebService\DynamicAssemblyLoading\SQLServer\bin\Debug\SQLServer.dll") Dim factory As Object = ass.CreateInstance("CRDataLayerFactory", True) Dim t As Type = factory.GetType Dim method As MethodInfo = t.GetMethod("Create") Dim obj As Object = method.Invoke(factory, Nothing) SQLDataSource = DirectCast(obj, ICRDataLayer) EDIT: Implementation based on Paul Kohler's code Dim file As String For Each file In Directory.GetFiles(baseDir, searchPattern, SearchOption.TopDirectoryOnly) Dim assemblyType As System.Type For Each assemblyType In Assembly.LoadFrom(file).GetTypes Dim s As System.Type() = assemblyType.GetInterfaces For Each ty As System.Type In s If ty.Name.Contains("ICRDataLayer") Then MsgBox(ty.Name) plugin = DirectCast(Activator.CreateInstance(assemblyType), ICRDataLayer) MessageBox.Show(plugin.ModuleName) End If Next I get the following error with this code: Unable to cast object of type 'SQLServer.CRDataSource.SQLServer' to type 'DynamicAssemblyLoading.ICRDataLayer'. The actual DLL is in a different project called SQLServer in the same solution as my implementation code. CRDataSource is a namespace and SQLServer is the actual class name of the DLL. The SQLServer class implements ICRDataLayer, so I don't understand why it wouldn't be able to cast it. Is the naming significant here, I wouldn't have thought it would be.

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• Calculating a Sample Covariance Matrix for Groups with plyr

  - by John A. Ramey

  I'm going to use the sample code from http://gettinggeneticsdone.blogspot.com/2009/11/split-apply-and-combine-in-r-using-plyr.html for this example. So, first, let's copy their example data: mydata=data.frame(X1=rnorm(30), X2=rnorm(30,5,2), SNP1=c(rep("AA",10), rep("Aa",10), rep("aa",10)), SNP2=c(rep("BB",10), rep("Bb",10), rep("bb",10))) I am going to ignore SNP2 in this example and just pretend the values in SNP1 denote group membership. So then, I may want some summary statistics about each group in SNP1: "AA", "Aa", "aa". Then if I want to calculate the means for each variable, it makes sense (modifying their code slightly) to use: > ddply(mydata, c("SNP1"), function(df) data.frame(meanX1=mean(df$X1), meanX2=mean(df$X2))) SNP1 meanX1 meanX2 1 aa 0.05178028 4.812302 2 Aa 0.30586206 4.820739 3 AA -0.26862500 4.856006 But what if I want the sample covariance matrix for each group? Ideally, I would like a 3D array, where the I have the covariance matrix for each group, and the third dimension denotes the corresponding group. I tried a modified version of the previous code and got the following results that have convinced me that I'm doing something wrong. > daply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) , , = 1 SNP1 1 2 aa 1.4961210 -0.9496134 Aa 0.8833190 -0.1640711 AA 0.9942357 -0.9955837 , , = 2 SNP1 1 2 aa -0.9496134 2.881515 Aa -0.1640711 2.466105 AA -0.9955837 4.938320 I was thinking that the dim() of the 3rd dimension would be 3, but instead, it is 2. Really this is a sliced up version of the covariance matrix for each group. If we manually compute the sample covariance matrix for aa, we get: [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 Using plyr, the following gives me what I want in list() form: > dlply(mydata, c("SNP1"), function(df) cov(cbind(df$X1, df$X2))) $aa [,1] [,2] [1,] 1.4961210 -0.9496134 [2,] -0.9496134 2.8815146 $Aa [,1] [,2] [1,] 0.8833190 -0.1640711 [2,] -0.1640711 2.4661046 $AA [,1] [,2] [1,] 0.9942357 -0.9955837 [2,] -0.9955837 4.9383196 attr(,"split_type") [1] "data.frame" attr(,"split_labels") SNP1 1 aa 2 Aa 3 AA But like I said earlier, I would really like this in a 3D array. Any thoughts on where I went wrong with daply() or suggestions? Of course, I could typecast the list from dlply() to a 3D array, but I'd rather not do this because I will be repeating this process many times in a simulation. As a side note, I found one method (http://www.mail-archive.com/[email protected]/msg86328.html) that provides the sample covariance matrix for each group, but the outputted object is bloated. Thanks in advance.

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• Choosing the right .NET architecture. WCF? WPF/Forms, ASP.NET (MVC)?

  - by Tommy Jakobsen

  I’m in the situation that I have to design and implement a rather big system from the bottom. I’m having some (a lot actually) questions about the architecture that I would like your comments and thoughts on. I don’t hope that I’ve written too much here, but I wanted to give you all an idea of what the system is. Quick info about the applications, read if you want: I can’t share much detail about the project, but basically it’s a system where we offer our customer a service to manage their users. We have a hotline where the users call and our hotline uses an (windows) application (intranet) to manage the user’s data, etc. The customer also has a web application where they can see reports, information about their business and users, and the ability to modify their data. Modifying data is not just user data like address and so, but also information about the products/services the user has, which can be complicated. The applications will be built on Microsoft .NET Framework 4, with a MS SQL Server 2008 database. There will be a few applications that have to access this database, such as: Intranet application (used by us and our hotline) Customer web application type 1 Customer web application type 2 Customer web application type n different applications) … Now my big problem is what .NET parts I should use for such a system. For the “backend” I’ve considered using Windows Communication Foundation: Would WCF be a good choice? The intranet application will be an application that has to edit lots of records in the database. It has to be easy to navigate using the keyboard (fast to work with). Has a feature such as “find customer, find that, lookup this, choose this and update that”. What would be the best choice to develop this application in? Would it be WPF or good old Windows Forms? I don’t need all of the fancy graphics features in WPF, like 3D, but the application has to look nice (maybe something like the new Visual Studio/Office tools). And the same question goes for the web pages. They have much the same work to do, but not as many features as the intranet application, and not the same amount of data (much less). That is my questions for now. I’m hoping to get a discussion going that will open my eyes to some of these technologies, helping me decide architecture to go with. I would like to say thanks in advance, and let you all know that any thoughts will be much appreciated.

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• MacRuby + Interface Builder: How to display, then close, then display a window again

  - by Derick Bailey

  I'm a complete n00b with MacRuby and Cocoa, though I've got more than a year of Ruby experience, so keep that in mind when answering - I need lots of details and explanation. :) I've set up a simple project that has 2 windows in it, both of which are built with Interface Builder. The first window is a simple list of accounts using a table view. It has a "+" button below the table. When I click the + button, I want to show an "Add New Account" window. I also have an AccountsController < NSWindowController and a AddNewAccountController class, set up as the delegates for these windows, with the appropriate button click methods wired up, and outlets to reference the needed windows. When I click the "+" button in the Accounts window, I have this code fire: @add_account.center @add_account.display @add_account.makeKeyAndOrderFront(nil) @add_account.orderFrontRegardless this works great the first time I click the + button. Everything shows up, I'm able to enter my data and have it bind to my model. however, when I close the add new account form, things start going bad. if I set the add new account window to release on close, then the second time I click the + button, the window will still pop up but it's frozen. i can't click any buttons, enter any data, or even close the form. i assume this is because the form's code has been released, so there is no message loop processing the form... but i'm not entirely sure about this. if i set the add new account window to not release on close, then the second time i click the + button, the window shows up fine and it is usable - but it still has all the data that i had previously entered... it's still bound to my previous Account class instance. what am I doing wrong? what's the correct way to create a new instance of the Add New Account form, create a new Account model, bind that model to the form and show the form, when I click the + button on the Accounts form? ... this is all being done on OSX 10.6.6, 64bit, with XCode 3.2.4

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• iPhone reachability checking

  - by Sneakyness

  I've found several examples of code to do what I want (check for reachability), but none of it seems to be exact enough to be of use to me. I can't figure out why this doesn't want to play nice. I have the reachability.h/m in my project, I'm doing #import <SystemConfiguration/SystemConfiguration.h> And I have the framework added. I also have: #import "Reachability.h" at the top of the .m in which I'm trying to use the reachability. Reachability* reachability = [Reachability sharedReachability]; [reachability setHostName:@"http://www.google.com"]; // set your host name here NetworkStatus remoteHostStatus = [reachability remoteHostStatus]; if(remoteHostStatus == NotReachable) {NSLog(@"no");} else if (remoteHostStatus == ReachableViaWiFiNetwork) {NSLog(@"wifi"); } else if (remoteHostStatus == ReachableViaCarrierDataNetwork) {NSLog(@"cell"); } This is giving me all sorts of problems. What am I doing wrong? I'm an alright coder, I just have a hard time when it comes time to figure out what needs to be put where to enable what I want to do, regardless if I want to know what I want to do or not. (So frustrating) Update: This is what's going on. This is in my viewcontroller, which I have the #import <SystemConfiguration/SystemConfiguration.h> and #import "Reachability.h" set up with. This is my least favorite part of programming by far. FWIW, we never ended up implementing this in our code. The two features that required internet access (entering the sweepstakes, and buying the dvd), were not main features. Nothing else required internet access. Instead of adding more code, we just set the background of both internet views to a notice telling the users they must be connected to the internet to use this feature. It was in theme with the rest of the application's interface, and was done well/tastefully. They said nothing about it during the approval process, however we did get a personal phone call to verify that we were giving away items that actually pertained to the movie. According to their usually vague agreement, you aren't allowed to have sweepstakes otherwise. I would also think this adheres more strictly to their "only use things if you absolutely need them" ideaology as well. Here's the iTunes link to the application, EvoScanner.

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• Which MarkDown (WMD) javascript editor should I use?

  - by Edan Maor

  Background I'm working on an application which requires user-entered content, and I've decided to use a StackOverflow-style MarkDown editor. After researching this topic for the last few days, I realize there are numerous forks of the base WMD editor, some with a few basic enhancements and some with serious differences from the StackOverflow one. Since this will be the heart of the application, I'd like to start with the best code base I can. I'd be happy if anyone can recommend which one of the many solutions out there best fits my needs. Below is requirements, plus what I've managed to find already. I'm hoping this question will help me decide which version to go with, and maybe help me discover a port out there that's an even better fit for my needs. The requirements for my project Live Preview Multiple editors on the same page (not know how many in advance, since the user can dynamically add another editing box). Ability to extend with extra buttons (I'd like a button to upload a picture, instead of just adding an img url). Ability to dynamically show/hide the edit box (and only see the preview box). Not an absolute must, but I'd prefer to stick as close to StackOverflow's look and feel, since it's well known. Don't know if this matters, but the backend is written in Django. Editors I've looked at Here are a few of the code bases I've looked at, with thoughts. Obviously, I might be missing another solution out there. The derobins version. From what I can tell, this is the official StackOverflow version. Seems like it doesn't support multiple editors on one page. JQuery.MarkEdit. Looks very good, but is pretty different from the StackOverflow version. MooWMD. Looks like the winner right now, but I'm a little concerned since it looks less active/hackable than MarkEdit. The wmd-new version. Not sure, looks like an old codebase without much use. The SocialSite branch. Seems like it's not for public use.

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